feat(chat): add auto-title generation after first exchange (M8.5)

After the first AI response, sends a background request to generate
a 3-5 word title using Claude Haiku. Silently replaces the default
title derived from the first user message.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/composables/useAI.ts

@@ -281,6 +281,51 @@ function formatWebSearchContext(results: { title: string; url: string; content?:
 
 let currentAbort: AbortController | null = null
 
+/** Background title generation after first exchange */
+async function generateAutoTitle(conversationId: string) {
+  const chatStore = useChatStore()
+  const conv = chatStore.conversations.get(conversationId)
+  if (!conv) return
+
+  // Only auto-title after first exchange (1 user + 1 assistant message)
+  if (conv.messages.length !== 2) return
+  const userMsg = conv.messages[0]
+  if (userMsg.role !== 'user') return
+
+  // Skip if title was manually set (not auto-generated from first message)
+  const autoTitle = userMsg.content.slice(0, 60) + (userMsg.content.length > 60 ? '...' : '')
+  if (conv.title !== autoTitle) return
+
+  try {
+    const headers: Record<string, string> = { 'Content-Type': 'application/json' }
+    const vaultKey = await getApiKey('claude')
+    if (vaultKey) headers['x-api-key'] = vaultKey
+
+    const res = await fetch(CLAUDE_PATH, {
+      method: 'POST',
+      headers,
+      body: JSON.stringify({
+        model: 'claude-haiku-4.5',
+        system: 'You generate very short conversation titles. Respond with ONLY a 3-5 word title, no quotes, no punctuation at the end.',
+        messages: [{ role: 'user', content: `Title this conversation: "${userMsg.content.slice(0, 200)}"` }],
+        max_tokens: 20,
+        stream: false,
+      }),
+    })
+
+    if (!res.ok) return
+
+    const data = await res.json()
+    const title = data?.content?.[0]?.text?.trim()
+    if (title && title.length > 0 && title.length < 60) {
+      conv.title = title
+      conv.updatedAt = Date.now()
+    }
+  } catch {
+    // Silent fail — title stays as default
+  }
+}
+
 export function useAI() {
   const chatStore = useChatStore()
 
@@ -353,6 +398,9 @@ export function useAI() {
       currentAbort = null
       chatStore.isStreaming = false
     }
+
+    // Auto-title: generate a short title after first exchange
+    generateAutoTitle(cid)
   }
 
   /**